Method of manufacturing an absorbent product



Oct- 1 19 A. A. BURGENI 2,955,641

METHOD OF MANUFACTURING AN ABSORBENT PRODUCT Filed Aug. 16, 1956INVENTOR I ,4; Page 4. fiz/Eqas/v/ BY l v 44mm T K ATTORNEY METHOD OFMANUFACTURING AN ABSORBENT PRODUCT Alfred A. Burgeni, Short Hills, N.J.,assignor to Personal Products Corporation, a corporation of New JerseyFiled Aug. 16, 1956, Ser. No. 604,540

9 claims, Cl. 15433) This invention relates to absorbent fibrous bodiesand to methods and apparatus for making them and, more particularly, isconcerned with absorbent fibrous bodies which are especially suited foruse as absorbent compoas a principal component thereof an absorbent pador core to absorb the fluids. These pads or cores are normally made oflayers of loosely compacted, absorbent fibers, such as carded cottonwebs, air-laid cellulosic fibrous webs, comminuted wood pulp bats, orlike materials which are highly absorbent, fluffy and porous. Un-

fortunately, these loosely compacted, fibrous absorbent bodies possessnumerous disadvantages, notably low cohesive strength, poor shape andvolume stability, low forces of capillary attraction, low fluidretentivity and low absorptive capacities under conditions of use.

For example, comminuted Wood pulp bats, which are particularly suitableas absorbent components because of their highly absorbent properties,low cost and commercial availability, are very weak structurally andpossess low cohesive stability,whereby they tend to fall apart tooreadily under stress.

Additionally, these comminuted wood pulp bats, as well as cotton fibrouswebs, do not possess shape and volume stability to any marked degree andquickly become deformed and distorted upon the application of slightforces or stresses.

Furthermore, the fluid retentivity of such highly porous, fibrousabsorbent bodies is not sufficiently great and, consequently, fluidswhich should beretained therein are squeezed out relatively easily bythe application of pressures arising from normal usage of the article.

Moreover, these fluffy, porous, absorbent fibrous components possess lowcapillary forces because of their 'loosely compacted structure and, whena fluid is deposited on its surface, saturation conditions are reachedvery quickly at the site of immediate application. At the .same time,however, the adjacent portions remain relaa considerable field forimprovement toward a superior product.

Incopending application Serial Number 587,015,filed on May 24, 1956,there are disclosed methods of manufacturing improved absorbent fibrousbodies which pos fluid retentivity. and high absorptive capacity undercon- 1ditions" of use and which are especially suited for use asabsorbent components in sanitary napkins, surgical dress- United StatesPatent .sess relatively high cohesive stability, good shape and volumestability, high forces of capillary attraction, good is separated fromthe pressure-applying means.

2,955,641 Patented Oct. 11, 1960 ice . 2 ings, compresses, disposablediapers, hospital underpads and other products designed to absorbfluids.

More specifically, the methods disclosed in said copending applicationcomprise applying controlled amounts of moisture to the surface orsurfaces of a loosely compacted, absorbent fibrous body havingrelatively low cohesive strength, relatively poor shape and volumestability, relatively low fluid retentivity and relatively low capillaryforces and then directly applying pressure thereto within controlledlimits whereby there is formed, in situ, a paper-like, densified, highlycompacted cellulosic fibrous layer integral with the loosely compacted,fibrous absorbent body and possessing relatively high cohesive strength,relatively good shape and volume stability, relatively highfluid-retentivity and relatively high capillary desirably controls thereception, absorption and retention of fluids deposited thereon.

The methods disclosed in said application for forming such a compactedlayer have been found generally satisfactory but it has been observedthat the compacted layer occasionally shows a tendency to adhere to thepressureapplying means and quite often stick thereto whereby it isripped loose from the absorbent fibrous body when it This sticking tothe pressure-applying means is, of .course, all the more accentuatedwhen a sharply contoured or specially shaped roller is used, such aswhen embossing.

'It is also more pronounced when certain chemical treat the absorbentfibrous body is facilitated.

These objects and others which will become clear her inafter areobtained by providing a protecting means comprising a fabricatedshielding web which is positioned .between the absorbent fibrous bodyand the pressureapplying means to prevent a direct contact .therebetweenduring the application of pressure and thus avoid any sticking oradhering tendencies.

In the accompanying drawing and the following specification there isillustrated and described a preferred method and apparatus for carryingout the present invention, but it is to be understood that the inventiveconcept is not to be construed as limited thereto except as defined bythe spirit of the invention and determined by the scope of the appendedclaims. Referring to the drawing:

Fig. l is a schematic showing of apparatus suitable for carrying out themethods of the present invention;

Fig. 2 is a fragmentary perspective view, on an enlarged scale, of ashielding web; and

a Fig. 3 is a perspective view of a product produced in spray nozzle 11to a non-coherent, loosely compacted,

absorbent fibrous body 12, moving to the right on an endless belt or ona table, as" shown in Fig. 1'. The

absorbent body 12 is guided under a rotating roller 13 which is capableof controllably applying a predetermined pressure thereto to. compactand, if desired, entobtuse angle.

boss the same. An endless shielding web 14 is guided around a drivingroller and guide rollers 16 and 17 so as to be inserted between theabsorbent body 12 and pressure roller 13 to prevent direct contactbetween the two during the application of pressure.

As set forth in the figure, the driving roller 15 and the guide rollers16 and 17 are so positioned that the shielding web 14 contacts theabsorbent body 12 in the vicinity of the pressure roller 13, travelstherewith for a short distance and then leaves the absorbent body at anNo sticking or adhering of the compacted layer 18 to the shielding Webis noted and there is no tendency of such layer to separate from thelesser compacted part of the absorbent fibrous body.

The angle at which the shielding web 14 leaves the treated absorbentfibrous body 12 is important and, al-

though the nature of the shielding web may be such and the conditions ofmoisture, application of pressure, etc., may be so selected that anacute angle of separation of less than 90 may be employed, an obtuseangle of greater than 90 and up to 180 is customarily used.Substantially the same effect is obtained by using a relatively smallroller for the guide roll 17 whereby the shielding web is quicklyremoved from contact with the absorbent fibrous body by being quicklypeeled backwardly therefrom at a small radius of curvature and at nozzle11 are characterized by their ability to produce or contribute to aperment set of the deformation achieved in compressing and/or embossingthe absorbent body. The object of the liquid setting agent is tostabilize the compressive deformation and to improve the coherence ofthe absorbent body. In the absence of such liquid setting agents, it isnecesary to apply much higher pressures to set the compressed absorbentbody. Moreover, dry compressed absorbent bodies remain substantiallynon-coherent and the set is largely lost in subsequent contact withwater and other swelling or treating agents.

The setting mechanism in the described operation is that of forminghydrate bonds between the wetted and compressed fibers which is awell-known and fundamental reaction in the process of paper making.Water is the most convenient and economical bonding fluid for cellulosicabsorbent bodies but it may be partially or completely replaced by otherstrongly polar fluids such as glycols, glycerol, sorbitol, etc. Ifdesired, the stabilizing effect of the water bond can be enhanced bywellknown textile sizing and finishing agents, such as natural andsynthetic gums, including starches, dextrins, casein, etc.,thermoplastic and thermo-setting resins including polyvinyl acetate,polyvinyl chloride, copolymers thereof,

etc., waxes, etc. These auxiliary processing agents are preferably usedin aqueous solution, suspension or dispersion.

The shielding webs may be woven, knitted, braided or felted fabricatedmaterials made from natural and/or synthetic fibers, monofilaments,multifilaments and staple yarn, and even of glass or flexible metallicwires. Fibers of high mechanical resistance made from nylon, Orlon,saran, saponified acetate rayon, and other flexand abrasion-resistancesynthetic materials may be used. A1- ternatively, such syntheticmaterials may be used in blends with naturally occurring yarns. Forexample, in the case of a woven fabric, the warp threads may be cottonand the filling or weft threads may be nylon, such as when longitudinallines are to be embossed into the absorbent body.

It is also to be noted that the shielding web itself is capable ofembossing the absorbent fibrous body. For example, a ribbed effect maybe obtained by using a twill cloth for the shielding web. Actually, anytype of fabricated material having a pronounced contoured surface can beused to create a complementary surface effect in the absorbent fibrousbody.

If increased stretchability is desired in the shielding web, it may beof knitted or specially Woven construction such as an elastic Helencawoven fabric. The shielding web may contain rubber threads, such asLastex, or the like. A fair degree of stretchability may also beobtained with mercerized-shrunk, natural cellulosic fabrics or by biascutting of woven cloth.

The absorbent fibrous bodies of this invention contain fibers of shortfiber length less than one-quarter of an inch, such as comminuated woodpulp fibers, cotton linters, or the like, which, in the presence ofmoisture and pressure, are capable of forming a relatively dense, moreor less coherent, relatively stable structure formed as a result ofinterfiber bonds between the moistened and compressed fibers similar tothe hydrate bonds. between fibers in paper. Cellulosic fibers, such aswood pulp fibers and cotton linters which have short fiber lengths asnoted above, are preferred in making the fibrous bodies of thisinvention because they readily form such interfiber bonds, whenmoistened and compressed. Such fibers are additionally commerciallydesirable inasmuch as they are inexpensive, readily available and highlyabsorbent. Other fibers capable of developing interfiber bonds, similarto the bonds between fibers in paper in the presence of moisture andpressure may also be used. In addition, natural or synthetic fibers,such as silk, wool, linen, nylon and cellulose acetate fibers, may beused in combination with the fibers capable of forming interfiber bondsin the presence of moisture and pressure.

It is believed that the formation of the densified skin is due to theformation of hydrate bonds between contacting moistened fibers, whichbonds are similar to the bonds between the fibers in paper. Ifadditional bonding is desired, then any sizing material such assynthetic resin, starch, etc., may be added to the aqueous processingliquid to increase the adhesion of the hydrate bonds. By the properselection of the amount of moisture applied to the fibers and by theproper selection of the degree of compression imposed, the properties ofthe densified skin may be varied, as desired or required. The thickness,density, strength and other characteristics of the densified skin alsodepend upon the uniformity by which the moisture is applied, the depthto which it penetrates and the degree to which the fibers arecompressed. For example, by finely spraying a web of wood pulp fibershaving a fiber length of less than inch with about 0.0015 cc. of waterper square centimeter of web surface and then exposing the web to apressure of, for instance, about 40 pounds per square inch, a densified,coherent, papery skin is obtained on the surface of the web which hadbeen moistened.

The amount of moisture used may vary from about 0.0005 to about 0.03 cc.of water per square centimeter of web surface depending upon thethickness of the Web, the thickness of the paper-like, densified skindesired, with the lesser amounts of moisture being used for thinner websand yielding extremely thin papery skins and the greater amounts ofmoisture being used for thicker webs and yielding skins of a greaterthickness.

Within the more commercial aspects of the present invention, however, ithas been found that a range of from about 0.001 to about 0.004 cc. ofwater per square or more pounds per square inch, with the commerl ciallypreferable range extending from about to about 100 pounds per squareinch.

An endless shielding Web belt, 70 mm. wide and weighing 125 grams persquare meter and made of bleached cotton print cloth was 'used underpressures of about 10 pounds and about 60 pounds per square inch in thepresence of 0.0015 cc. of water per square centimeter. Such methodsresulted in the conversion of lesser and greater proportionsrespectively of the original web into the dense paper-like layers.

The use of moistures of 0.001 and 0.003 cc. per square centimeter wasevaluated with a shielding web of Helenca elastic nylon woven fabricunder a pressure of about 40 pounds per square inch. The lesser amountof moisture (0.001) yielded an extremely thin, papery layer whereas thegreater amount of moisture (0.003) yielded a heavier bonded layerusablewhere such density and strength was desirable.

Another trial was made under similar conditions but increasing themoisture to 0.004 cc. of Water vapor per square centimeter of websurface and using a smooth, densely woven twill fabric made of nylon,rayon and cellulose acetate, weighing 305 grams per square meter. Thistime the compacted layer was considerably thicker than that obtainedpreviously and the thickness of the completed integral web was reducedcorrespondingly. Still another trial was made under similar conditions,

using a knitted light cotton tricot weighing 214 grams per square meteras the shielding web but using a very heavy spray of water. Theresulting article was stronger and more cardboard-like and well suitedfor uses and purposes where such characteristics were desired.

The moisture or liquid may also be applied so as to penetrate completelythrough the absorbent fibrous body and conversion to a more solid bodymay then be accomplished by the application of suflicient pressure.

From the above, it is seen that loosely compacted absorbent fibrousbodies, whichfpossess relatively low cohesive'strength, relatively poorshape and volume stability, relatively low fluid retentivity, andrelatively low capillarity, are converted to bodies possessing arelatively dense, compacted, coherent skin which creates suflicientstrength, shape and volume stability, fluid retentivity, andcapi'llarityas to render the resulting structure especially suited and highlydesirable for use as absorbent components in surgical dressings,sanitary napkins, compresses, disposable diapers, hospital underpads,and other products designed to absorb body fluids.

It is, of course, realized that various modifications and changes may bemade Within the spirit of the in- 6 greater strength, shape "and volumestability, fluid retentivity and capillarity are desired or required.

While I have shown and described what I believe to be preferredembodiments of my invention in the matter of simplicity and durabilityof construction, it will be appreciated that the details of suchconstruction may be more or less. modified within the scope of theclaims without departure from the principles of construction or materialsacrifice of the advantages of the preferred designs.

I claim:

1. The method of producing an absorbent component for use in anabsorbent product which comprises forming dry a highly porous, looselycompacted, absorbent fibrous body containing cellulosic fibers shorterthan onequarter of an inch, 'said body having low cohesive strength, lowcapillarity, poor shape and volume stability, and low fluid retentivity,applying moisture to the body to moisten only the surface portionthereof, positioning a shielding web on the moistened surface of saidbody, applying pressure to said body through said shielding web to formin the moistened surface portion of said body an integral, densified,compacted, porous, absorbent fibrous layer having high cohesivestrength, increased capillarity, good shape and volume stability andhigh fluid retentivity.

2. The method of producing an absorbent component for use in anabsorbent product which comprises forming dry a highly porous, looselycompacted, absorbent fibrous body containing cellulosic fibers shorterthan onequarter of an inch, said body having low cohesive strength, lowcapillarity, poor shape and volume stability, and low fluid retentivity,applying moisture to the body to moisten only the surface portionthereof with from about 0.0005 to about 0.03 cc. of water per squarecentimeter of surface area, positioning a shielding web on the moistenedsurface of said body, applying pressure to said body through saidshielding web to form in the moistened surface portion of said body anintegral, densified, compacted, porous, absorbent fibrous layer havinghigh cohesive strength, increased capillarity, good shape and volumestability and high fluid retentivity, and separating said shielding webfrom said body.

3. The method of producing an absorbent component for use in anabsorbent product which comprises forming dry a highly porous, looselycompacted, absorbent fibrous body containing cellulosic fibers shorterthan one-quarter of an inch, said body having low cohesive strength, low

vention. For example, various materials such as highly absorbent Waddingpaper, gauze, non-woven fabrics, and the like, may be placed on thehumidified or wetted web surface so that, after the pressure has beenapplied, the materials become integral with the thin paper-like skinwhich is formed.

It is also contemplated that various materials such as bactericides,fungicides, dyestuffs, softening agents, sizing materials, adhesives,and the like, may be included in the water used for moistening thesurfaces of the webs. These processes reflect the well-knownpossibilities of mechanically modifying paper to obtain desired results.Additionally, if desired, a second spray nozzle may be employed oppositenozzle 11, or the entire apparatus set forth in the figure may beduplicated on the other side of the absorbent fibrous body 12 (belowbody 12 in the figure) whereby two dense, compacted layers are formed,one on each surface of the absorbent fibrous body 12. The resultingproduct is of application where capillarity, poor shape and volumestability, and low fluid retentivity, applying moisture to the body tomoisten only the surface portion thereof with from about 0.0005 to about0.03 cc. of water per square centimeter of surface area, positioning ashielding web on the moistened surface of said body, applying from about5 to about pounds per square inch of pressure to said body through saidshielding web to form in the moistened surface portion of said body anintegral, densified, compacted, porous, absorbent fibrous layer havinghigh cohesive strength, increased capillarity, good shape and volumestability and high fluid retentivity, and separating said shielding webfrom said body.

4. The method of producing an absorbent component for use in anabsorbent product which comprises forming dry a highly porous, looselycompacted, absorbent fibrous body containing cellulosic fibers shorterthan one-quarter 7 stability and high fluid retentivity, and separatingsaid shielding web from said body.

The method of producing an absorbent component for use in an absorbentproduct which comprises forming dry a highly porous, loosely compacted,absorbent fibrous body containing cellulosic fibers shorter thanone-quarter of an inch, said body having low cohesive strength, lowcapillarity, poor shape and volume stability, and low fluid retentivity,applying moisture to the body to moisten only the surface portionthereof, positioning a shielding web in the form of a knitted fabric onthe moistened surface of said body, applying pressure to said bodythrough said shielding web to form in the moistened surface portion ofsaid body an integral, densified, com- -pacted, porous, absorbentfibrous layer having high cohesive strength, increased capillarity, goodshape and volume stability and high fluid retentivity, and separatingsaid shielding web from said body.

6 The method of producing an absorbent component for use in an absorbentproduct which comprises forming dry a highly porous, loosely compacted,absorbent fibrous body containing cellulosic fibers shorter thanone-quarter of an inch, said body having low cohesive strength, low

capillarity, poor shape and volume stability, and low fluid retentivity,applying moisture to the body to moisten only the surface portionthereof, positioning a shielding web on the moistened surface of saidbody, applying pressure to said body through said shielding web to formhydratebonds between fibers in the moistened surface portion of saidbody and to form an integral, densified, compacted, porous, absorbentfibrous layer having high cohesive strength, increased capillarity, goodshape and volume stability and high fluid retentivity, and separatingsaid shielding web from said body.

7. The method of producing an absorbent component for use in anabsorbent product which comprises forming dry a highly porous, looselycompacted, absorbent fibrous body containing cellulosic fibers shorterthan one quarter of an inch, said body having low cohesive strength, low

capillarity, poor shape and volume stability, and low fluid retentivity,applying moisture to the body to moisten only the surface portionthereof, positioning a patterned shielding web on the moistened surfaceof said body, applying pressure to said body through said shielding webto form in the moistened surface portion of said body anintegral,densified, compacted, porous, absorbent fibrous layer having highcohesive strength, increased capillarity, good shape and volumestability and high fluid retentivity, and separating said shielding webfrom said body.

.8. The method of producing an absorbent component for use in anabsorbent product which comprises forming dry a highly porous, looselycompacted, absorbent fibrous body containing cellulosic fibers shorterthan one-quarter of an inch, said body having low cohesive strength, lowcapillarity, poor shape and volume stability, and low fluid retentivity,applying moisture to the body to moisten only the surface portionthereof, positioning a shielding Web on the moistened surface of saidbody, applying pressure to said body through said shielding web bypassing said body and said web through a rotating pressure roll to formin the moistened surface portion of said body an integral, densified,compacted, porous, absorbent fibrous layer having high cohesivestrength, increased capillarity, good shape and volume stability andhigh fluid retentivity, and separating said shielding web from saidbody.

9. The method of producing an absorbent component for'use in anabsorbent product which comprises forming dry a highly porous, looselycompacted, absorbent fibrous body containing cellulosic fibers shorterthan one-quarter of an inch, said body having low cohesive strength, low

capillarity, poor shape and volume stability, and low fluid retentivity,advancing said body, applying moisture to the body to moisten only thesurface portion thereof,

positioning an endless shielding web on the moistened surface of saidbody, said web advancing at the same rate as said body, applyingpressure by means of roller devices to said body through said shieldingweb to form in the moistened surface portion of said body an integral,densified, compacted, porous, absorbent fibrous layer having highcohesive strength, increased capillarity, good shape and volumestability and high fluid retentivity,

separating said shielding web from said body, and guiding said shieldingweb in an endless closed circuit so as to have a portion thereofcontinuously positioned between said absorbent fibrous body and saidroller devices for applying pressure.

References Cited in the file of this patent UNITED STATES PATENTS

